Rachel Bilson reappeared in the latest episode of "How I Met Your Mother."

Rachel Bilson has offered clues to How I Met Your Mother's top secret. The entire CBS show revolves around character, Ted, explaining to his kids how he came to meet their mother.

However, after eight seasons of the show the identity of the mother is still a mystery, with the show continually dropping clues to viewers to help them try to figure out who it could be.

Former star of "OC", Rachel Bilson, has become the center of new hints on the show. Bilson first made an appearance on the hit sit-com show back in 2010, and was introduced as a girl who Ted met when he was teaching. Part of her early storyline was that she dated Ted for a short while.

Her character, Cindy, was later confirmed not to be Ted's future wife, but she was identified as the future wife's roommate.

In a recent episode Cindy drops a number of hints to help fans identify the mother. In the show Ted realizes that he will never be with long-time interest, Robin, and he then attempts to take over the wedding planning.

The episode unravels with an argument about whether a DJ should be used or a live band. It eventually pans out that Barney and Robin really want a live band - however, the band cancels at the last minute.

In a sudden twist Ted meets up with Cindy and learns that her former roommate is the bass player for "the best wedding band in the tristate area." The band is available, and viewers are left with a huge clue as to who the mother could be.

Past hints on the show have revealed that the eventual spouse of Ted has a yellow umbrella, and is part of their coming together. It was also revealed in Season 3 that Barney and Ted attended a big St Patrick's Day party, where his future wife was also attending.

In other clues, the future wife has been identified as an economics student, and he meets her on the day of Barney and Robin's wedding, as she is playing the wedding band booked at the last minute.

It is also known that Ted and his future wife have a daughter by 2015, and that the couple officially met at the Farhampton train station after Barney and Robin's wedding. Apparently she is holding a yellow umbrella to keep out of the rain.